The new custom reporting system is far worse than the old custom reporting. Less intuitive, less flexible, and can output incorrect information.

There is no method for reporting on some combination of Users / Teams / Courses. Under the custom reporting for Learning Paths, I found I could include Users and Courses, but the output is garbage - a course assigned to one Learning Path that is assigned to one Team, is reported five times against each of the five Teams the User is assigned to.